Defending champion Roger Federer pulled out of his semi-final match against Jo-Wilfried Tsonga at the Qatar Open because of a back injury yesterday but said he expects to be fit for the Australian Open. In a news conference held 30 minutes before his match was scheduled, the 16-time Grand Slam champion said his back had not improved since beating Andreas Seppi in three sets on Thursday. Federer, who was looking for his fourth title in Doha, apologised to organisers but said he didn\'t want to risk further injury ahead of the Australian Open. It is only the second time the 30-year-old Swiss has pulled out of a tournament due to injury in his illustrious career. ‘Only right decision\' \"I don\'t feel a whole lot of improvement for today, and I just don\'t think it\'s the right time to risk anything more right now,\" Federer said. \"I still have pain, and that\'s why it was the only right decision, a difficult one for me... So it\'s a sad moment for me and for the tournament and for the fans, but health goes first.\" Federer said he has tried several treatments including massage and baths after he first felt the injury during his second round match against qualifier Grega Zemlja. He played against Seppi but struggled to a three-set victory, trailing 5-1 during the second set and looking out of sorts. But afterward, he said nothing about the injury. \"It came throughout two points against Zemlja in the beginning, 2-1 in the first set, and then I wasn\'t able to serve properly anymore,\" Federer said. \"For Australia, I\'m optimistic, just because it\'s not very good but it isn\'t crazy bad. \"I have had bad backs in the past. I feel without play and the right treatment, I will get through it in the next few days.\"